In a refrigeration system, it is well understood that air and non-condensable gases (herein after air refers to both air and non-condensable gases) can produce high head pressures and cause the compressor to operate at higher than normal temperatures. Air can react with the refrigerant and oil at the head of the compressor and cause decomposition and the formation of acids (hydrofluoric and hydrocloric). Air can be trapped in the upper space of the receiver or can circulate through the system, induced by the velocity of the refrigerant. In the evaporator or the condenser, air can interfere with the heat exchange process.
Air can be present in a system because of incomplete evacuation after pressure testing with nitrogen, by leakage of air into a system that operates under a vacuum and by the seepage of air into the system when opened for the repair or replacement of a component. In most cases, the customary method of removing air is to manual purge at the location where the system was opened or to pump down the system, shut off the compressor and manual purge from the top of the condenser. This is wasteful as refrigerant is released with the air and contaminates the atmosphere. Therefore, it is necessary that more efficient methods of purging be used. U.S. Pat. Nos. 2,920,458 and 4,776,175 show a purging method and apparatus using a cooling means such as circulating cold water or refrigerant from a secondary refrigerating machine through a coil or jacket of a purger vessel for the purpose of condensing the refrigerant gas entering the purger. Air collects in the upper portion of the purger, displacing the contact of the condensable gas at the cooling coil causing a lowering of the temperature at the coil outlet. Pressure or temperature sensing means actuate a solenoid operated purging valve to discharge air from the purger when these lower conditions occur. These purgers must be permanently located at an elevation above the receiver to allow drainage of the condensed liquid refrigerant back through a two phase conduit to the receiver. This limits the purger to use on one system as they are piped in and the bulk and weight of the purger would make it not practical to move.
Many fluorocarbon refrigeration applications such as in supermarkets use multiple systems of single compressors or of multiple compressors connected in parallel. Typically there are from two to six or more systems in one supermarket. Therefore an efficient purger that is portable and easily hooked up is needed.